Apparatus, method, and composition for far edge wafer cleaning

ABSTRACT

A wafer cleaning apparatus includes a polishing unit used in chemical mechanical polishing (CMP) of a wafer and a cleaning dispensing unit arranged to direct cleaning fluids toward a far edge of the wafer after the CMP of the wafer. A wafer cleaning method includes CMP of a wafer by a polishing unit and directing cleaning fluids toward a far edge of the wafer after the CMP of the wafer by a cleaning dispensing unit. Another method can include CMP, applying deionized water, and applying pH adjuster having a pH range from about 2 to about 13.

TECHNICAL FIELD

The disclosure is related to a method, apparatus and composition used incleaning far edges of wafers used in semiconductor devices.

BACKGROUND

Chemical mechanical polishing, CMP, is commonly used in thesemiconductor manufacturing industry to polish and remove metal or othermaterials from over a surface of a semiconductor substrate upon whichsemiconductor devices are being fabricated. Most commonly, conductiveinterconnect patterns are formed on semiconductor devices by forming aseries of openings, such as vias and trenches in an insulating materialdisposed on a substrate surface, and then forming a conductive layerover the substrate surface and filling the openings. Damascenetechnology involves removing the conductive material from over thesurface such that the conductive material remains only in the openingsto form conductive structures such as various plugs and leads that serveas interconnection patterns and vias. CMP is also used extensively forplanarizing shallow trench isolation regions.

When polishing to remove metal materials from over the substratesurface, it is critical to ensure that no metal residue remains over thesurface as this can cause bridging between otherwise isolated conductivefeatures, resulting in short circuits. Even when additional steps suchas brush cleaning are used after CMP, residues remain that can stillcause defects.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read in conjunction with the accompanying drawings. Itis emphasized that, according to common practice, the various featuresof the drawings are not necessarily to scale. On the contrary, thedimensions of the various features can be arbitrarily expanded orreduced for clarity. Like numerals denote like features throughout thespecification and drawing.

FIG. 1 is a system depicting an existing wafer cleaning system;

FIG. 2 is a top view showing a number of defects in a wafer after usingthe cleaning system of FIG. 1;

FIG. 3 is a system and flow diagram depicting a wafer cleaning systemthat further cleans a far edge of a wafer in accordance with theembodiments herein; and

FIG. 4 is a further detailed view of the system and flow diagram of FIG.3; and

FIG. 5 is a flow chart depicting a method in accordance with theembodiments herein.

DETAILED DESCRIPTION

The disclosure provides a wafer cleaning apparatus including a polishingunit used in CMP of a wafer and a cleaning dispensing unit arranged todirect cleaning fluids toward a far edge of the wafer after the CMP ofthe wafer.

The disclosure also provides a method for wafer cleaning including CMPof a wafer by a polishing unit and directing cleaning fluids toward afar edge of the wafer after the CMP of the wafer by a cleaningdispensing unit.

The disclosure further provides a method of applying a chemicalcomposition toward a far edge of a wafer, the method including CMP ofthe wafer, applying deionized water to the wafer, and applying acleaning chemical containing pH adjuster, such as one or more of HNO₃,H₂SO₄, NH₄OH, KOH or organic amine, the cleaning chemical used after CMPof the wafer and being an acid or an alkaline having a pH range fromabout 2 to about 13.

It should be understood that the proceeding examples are intended to beexemplary only and other cleaning apparatus, methods, and chemicalcompositions can be used in other exemplary embodiments and furthercomponents can also be included in the various embodiments.

FIG. 1 is a system 100 depicting an existing wafer cleaning system thatincludes two separate enclosures for CMP of a wafer 105. ChemicalMechanical Polishing/Planarization (CMP) is a process of smoothingsurfaces with the combination of chemical and mechanical forces. A firstenclosure 102 can use an abrasive and corrosive chemical slurry(commonly a colloid) in conjunction with a polishing pad and retainingring to remove material such as copper from the surface of the wafer. Asecond enclosure 104 can similarly use a chemical slurry to furtherpolish and remove barriers and oxide insulator (oxide and low dielectricconstant material) on the wafer 105 as is known in the art. The post-CMPprocesses can include a brush cleaning process 106 which can beperformed twice in a first brush cleaning process 107 and a second brushcleaning process 108. The processes 107 and 108 can be identical. Thebrush cleaning process can be followed by a pencil cleaning process 110and a drying process 112 as illustrated.

Typical CMP tools comprise a rotating and extremely flat platen which iscovered by a pad. The wafer that is being polished is mountedupside-down in a carrier/spindle on a backing film. A retaining ringkeeps the wafer in the correct horizontal position. During the processof loading and unloading the wafer onto the tool, the wafer can be heldby vacuum by the carrier to prevent unwanted particles from building upon the wafer surface. A slurry introduction mechanism deposits theslurry on the pad. Both the platen and the carrier can then be rotatedand the carrier is kept oscillating as well. A downward pressure or downforce is applied to the carrier, pushing it against the pad. In CMP, themechanical properties of the wafer itself are considered too. If thewafer has a slightly bowed structure, the pressure will be greater onthe edges than it would on the center, which causes non-uniformpolishing. In order to compensate for the wafer bow, pressure can beapplied to the wafer's backside which, in turn, will equalize thecentre-edge differences. The pads used in the CMP tool should be rigidin order to uniformly polish the wafer surface. However, these rigidpads are kept in alignment with the wafer at all times. Therefore, realpads are often just stacks of soft and hard materials that conform towafer topography to some extent. Generally, these pads are made fromporous polymeric materials with a pore size between about 30 and about50 μm, are consumed in the process, and are regularly reconditioned. Theuse of copper conductors on wafers since about 1990 led to thedevelopment of an additive patterning (damascene) process, which relieson the abilities of CMP to remove material in a planar and uniformfashion and to stop repeatably at the interface between copper and oxideinsulating layers. Adoption of this process has made CMP processing muchmore widespread, but the CMP process remains a “dirty” process.

FIG. 2 depicts a polished and cleaned wafer 200 with defects 202 thathas gone through the processes illustrated in FIG. 1. Even afterpolishing, brush cleaning, pencil cleaning and drying, the underlyingwafer 150 will still have far edge organic residue forming the defects202.

FIG. 3 depicts a wafer cleaning apparatus 300 similar in some respectsto the wafer cleaning apparatus 100 of FIG. 1 since it includes at leasta CMP portion (102 and 104). But the wafer cleaning apparatus 300further includes a cleaning dispensing unit (302 or 304 or 306) arrangedto direct cleaning fluids toward a far edge of the wafer after the CMPof the wafer. The wafer cleaning apparatus 300 can also include post CMPprocesses such as the brush cleaning process 106 which can be performedtwice in a first brush cleaning process 107 and a second brush cleaningprocess 108 followed by a pencil cleaning process 110 and a dryingprocess 112 as illustrated.

The cleaning dispensing unit or units 302, 304, and 306 can be arrangedand placed in a number or locations within the overall wafer cleaningapparatus 300 in various embodiments. The cleaning dispensing unit orunits can be arranged outside of the enclosure or enclosures for thepolishing unit or units or the CMP processes (102 and 104). In oneembodiment, the cleaning dispensing unit 302 can be arranged ex-situ ofthe polishing units in a new chamber or enclosure before the brushcleaning process 106. In another embodiment, a cleaning dispensing unit304 can reside within (in-situ) an enclosure 107 or 108 for brushcleaning after the CMP. In yet another embodiment, a cleaning dispensingunit 306 can be arranged outside (ex-situ) after the enclosure(s) (102and 104) for CMP and outside (ex-situ) and after the enclosure(s) (107and 108) for brush cleaning. Again, the cleaning dispensing unit 306 canbe in a new chamber after brush cleaning.

Of course, other arrangements or permutations or combinations can bemade in accordance with the embodiments where one or more of thecleaning dispensing units (302, 304, or 306) are placed within theoverall wafer cleaning apparatus 300. In one embodiment, the wafercleaning apparatus 300 could include a first cleaning dispensing unit(304) within brush clean enclosure 107 or 108 and a second cleaningdispensing unit arranged outside and after an enclosure for CMP (302) oroutside and after the enclosure for brush cleaning (306). In yet anotherembodiment, the wafer cleaning apparatus 300 could include at least afirst cleaning dispensing unit (304) within the brush cleaning process(106), a second cleaning dispensing unit (302) arranged outside theenclosure(s) (102 and 104) for the polishing unit and a third cleaningdispensing unit (306) arranged outside the enclosure(s) (107 and 108)for brush cleaning. Further note that all the embodiments can furtherinclude not only one cleaning dispensing unit within the brush cleaningprocess 106, but can include one or more cleaning dispensing units foreach enclosure (107 and 108) of the brush cleaning process 106. Theembodiment illustrated in FIG. 3 can include a first cleaning dispensingunit (302) after CMP, a second cleaning dispensing unit (304) within theenclosure (107) for brush cleaning, a third cleaning dispensing unitwith the enclosure (108) for brush cleaning, and a fourth cleaningdispensing unit (306) after brush cleaning (106).

The cleaning dispensing units can be made of various materials and arenot limited to the materials disclosed herein. For example, the cleaningdispensing units (302, 304 or 306) can be made of a sponge materialcomprising of Polyvinyl Alcohol (PVA), Polyvinyl Chloride (PVC),Polyurethene (PU), or Polyethylene Terephthalate (PET). The spongematerial can have a porosity of about 30% to about 90%. In otherembodiments, the sponge material can have a pore size of about 20 toabout 200 micrometers. The cleaning dispensing units can also come in aform of a sponge having an concentric tube with inner chemical flow-in.In yet another embodiment, the cleaning dispensing unit can comprise ahigh pressure fluid jet. As illustrated in the wafer cleaning apparatus400 of FIG. 4, each of the cleaning dispensing units can come in theform of a sponge 402 or a high pressure fluid jet 404. The wafercleaning apparatus 400 is essentially the same as the wafer cleaningapparatus 300 of FIG. 3, except that each of the cleaning dispensingunits can optionally be either a sponge (402) or a high pressure fluidjet (404). In one embodiment, the wafer cleaning apparatus 400 can justinclude sponges and in another embodiment the wafer cleaning apparatus400 can just include high pressure fluid jets. In yet other embodiments,a combination of sponges and jets could be used.

In one example, the high pressure fluid jet (or the sponge) can use acleaning chemical having a pH range from about 2 to about 13. Thesurface tension of the cleaning chemical can have a range of about 20 toabout 70 dyne/cm, and a conductivity of the cleaning chemical can have arange of about 100 to about 4000 us/cm.

The chemical composition applied toward the far edge of the wafer (150)after CMP of the wafer can include deionized water and a cleaningchemical containing pH adjuster such as one or more of HNO₃, H₂SO₄,NH₄OH, KOH or organic amine, the cleaning chemical used after CMP of thewafer and being an acid or an alkaline having a pH range from about 2 toabout 13. In one embodiment, the cleaning chemical can contain a pHadjuster such as a combination of two among HNO₃, H₂SO₄, NH₄OH, KOH andorganic amine. As mentioned above, the surface tension of the cleaningchemical can have a range of about 20 to about 70 dyne/cm and theconductivity of the cleaning chemical can have a range of about 100 toabout 4000 us/cm.

Referring to FIG. 5, a flow chart illustrates a wafer cleaning method500. The method can include CMP of a wafer by a polishing unit at 502and directing cleaning fluids toward a far edge of the wafer after theCMP of the wafer by a cleaning dispensing unit at 504. Directingcleaning fluids towards the far edge can be done in a number of ways. Inone embodiment at 506, directing cleaning fluid can be done by applyinga sponge towards the far edge of the wafer after CMP and outside anenclosure used for CMP. In another embodiment at 508, directing cleaningfluids towards the far edge of the wafer can be done by applying asponge towards the far edge of the wafer after CMP, outside an enclosureused for CMP, and within an enclosure for brush cleaning. In anotherembodiment at 510, directing cleaning fluids towards the far edge of thewafer can be done by applying a first sponge towards the far edge of thewafer after CMP, outside an enclosure used for CMP, and applying atleast a second sponge towards the far edge of the wafer within anenclosure for brush cleaning. In yet another embodiment at 512,directing cleaning fluids towards the far edge of the wafer can be doneby applying a first sponge towards the far edge of the wafer after CMP,outside an enclosure used for CMP, applying at least a second spongetowards the far edge of the wafer within an enclosure for brushcleaning, and applying at least a third sponge towards the far edge ofthe wafer after CMP and brush cleaning and outside the enclosure forbrush cleaning.

In some embodiments, a wafer cleaning apparatus comprises a polishingunit used in CMP of a wafer. A cleaning dispensing unit is arranged todirect cleaning fluids toward a far edge of the wafer after the CMP ofthe wafer.

In some embodiments, a wafer cleaning method, comprises CMP of a waferby a polishing unit; and directing cleaning fluids toward a far edge ofthe wafer after the CMP of the wafer by a cleaning dispensing unit.

In some embodiments, a method of applying a chemical composition towarda far edge of a wafer comprises CMP of the wafer, applying deionizedwater to the wafer, and applying a cleaning chemical comprising at leastone of HNO₃, H₂SO₄, NH₄OH, KOH or organic amine. The cleaning chemicalis used after the CMP of the wafer and being an acid or an alkalinehaving a pH range from about 2 to about 13.

The preceding merely illustrates the principles of the disclosure. Itwill thus be appreciated that those skilled in the art will be able todevise various arrangements which, although not explicitly described orshown herein, embody the principles of the disclosure and are includedwithin its spirit and scope. For example the disclosed cleaningdispensing unit can use other materials other than the disclosed spongesand fluid jets.

Furthermore, all examples and conditional language recited herein areprincipally intended expressly to be only for pedagogical purposes andto aid in understanding the principles of the disclosure and theconcepts contributed by the inventors to furthering the art, and are tobe construed as being without limitation to such specifically recitedexamples and conditions. Moreover, all statements herein recitingprinciples, aspects, and embodiments, as well as specific examplesthereof, are intended to encompass both structural and functionalequivalents thereof. Additionally, it is intended that such equivalentsinclude both currently known equivalents and equivalents developed inthe future, i.e., any elements developed that perform the same function,regardless of structure.

This description of the exemplary embodiments is intended to be read inconnection with the figures of the accompanying drawing, which are to beconsidered part of the entire written description. In the description,relative terms such as “lower,” “upper,” “horizontal,” “vertical,”“above,” “below,” “up,” “down,” “before”, “after”, “top” and “bottom” aswell as derivatives thereof (e.g., “horizontally,” “downwardly,”“upwardly,” etc.) should be construed to refer to the orientation asthen described or as shown in the drawing under discussion. The drawingsare arbitrarily oriented for convenience of description and do notrequire that the apparatus be constructed or operated in a particularorientation. Terms concerning attachments, coupling and the like, suchas “connected” and “interconnected,” refer to a relationship whereinstructures are secured or attached to one another either directly orindirectly through intervening structures, as well as both movable orrigid attachments or relationships, unless expressly describedotherwise.

Although the disclosure has been described in terms of exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be construed broadly, to include other variants and embodiments,which can be made by those skilled in the art without departing from thescope and range of equivalents.

What is claimed is:
 1. A wafer cleaning apparatus, comprising: apolishing unit for chemical mechanical polishing (CMP) of a wafer and acleaning dispensing unit, wherein the polishing unit for CMP is arrangedto feed the wafer from an unload location of the polishing unit for CMPto the cleaning dispensing unit; and the cleaning dispensing unit isarranged to receive the wafer from the unload location of the polishingunit for CMP, and the cleaning dispensing unit comprises a fluid jetarranged to direct cleaning fluids directly from the fluid jet to a faredge of the wafer, after the wafer is transmitted from the polishingunit for CMP to the cleaning dispensing unit, wherein the cleaningdispensing unit resides within a first enclosure for brush cleaningafter the CMP.
 2. The wafer cleaning apparatus of claim 1, furthercomprising an additional cleaning dispensing unit arranged outside of anenclosure for the polishing unit.
 3. The wafer cleaning apparatus ofclaim 1, wherein the cleaning dispensing unit comprises a spongematerial comprising of Polyvinyl Alcohol (PVA), Polyvinyl Chloride(PVC), Polyurethene (PU), or Polyethylene Terephthalate (PET).
 4. Thewafer cleaning apparatus of claim 1, wherein the cleaning dispensingunit comprises a sponge material having a porosity of about 30% to about90%.
 5. The wafer cleaning apparatus of claim 1, wherein the cleaningdispensing unit comprises a sponge material having a pore size of about20 to about 200 micrometers.
 6. The wafer cleaning apparatus of claim 1,wherein the fluid jet uses a cleaning chemical having a pH range fromabout 2 to about
 13. 7. The wafer cleaning apparatus of claim 1, whereinthe fluid jet uses a cleaning chemical having a surface tension in arange of about 20 to about 70 dyne/cm.
 8. The wafer cleaning apparatusof claim 1, wherein the fluid jet uses a cleaning chemical having aconductivity in a range of about 100 to about 4000 μs/cm.
 9. A wafercleaning method using the apparatus of claim 1, comprising: chemicalmechanical polishing (CMP) of the wafer by the polishing unit; anddirecting cleaning fluids toward the far edge of the wafer after the CMPof the wafer by the cleaning dispensing unit.
 10. The wafer cleaningmethod of claim 9, wherein directing cleaning fluids towards the faredge of the wafer comprises applying a sponge towards the far edge ofthe wafer after CMP and outside an enclosure used for CMP.
 11. The wafercleaning method of claim 9, wherein directing cleaning fluids towardsthe far edge of the wafer comprises applying a sponge towards the faredge of the wafer after CMP, outside an enclosure used for CMP, andwithin an enclosure for brush cleaning.
 12. The wafer cleaning method ofclaim 9, wherein directing cleaning fluids towards the far edge of thewafer comprises applying a first sponge towards the far edge of thewafer after CMP, outside an enclosure used for CMP, and applying atleast a second sponge towards the far edge of the wafer within anenclosure for brush cleaning.
 13. The wafer cleaning method of claim 9,wherein directing cleaning fluids towards the far edge of the wafercomprises applying a first sponge towards the far edge of the waferafter CMP, outside an enclosure used for CMP, applying at least a secondsponge towards the far edge of the wafer within an enclosure for brushcleaning, and applying at least a third sponge towards the far edge ofthe wafer after CMP and brush cleaning and outside the enclosure forbrush cleaning.
 14. A method of applying a chemical composition toward afar edge of a wafer using the apparatus of claim 1, the methodcomprising: chemical mechanical polishing (CMP) of the wafer; applyingdeionized water to the wafer, and applying a cleaning chemical to thewafer, the cleaning chemical comprising at least one pH adjuster amongHNO₃, H₂SO₄, NH₄OH, KOH or organic amine, the cleaning chemical being anacid or an alkaline having a pH range from about 2 to about
 13. 15. Themethod of claim 14, wherein the cleaning chemical contains a combinationof at least two of HNO₃, H₂SO₄, NH₄OH, KOH and organic amine.
 16. Thewafer cleaning apparatus of claim 1, wherein the cleaning dispensingunit comprises a tube with inner chemical flow-in.
 17. The wafercleaning apparatus of claim 1, further comprising a second cleaningdispensing unit within a second enclosure for brush cleaning after thefirst enclosure for brush cleaning.
 18. The wafer cleaning apparatus ofclaim 17, further comprising a third cleaning dispensing unit.
 19. Thewafer cleaning apparatus of claim 17, wherein each of the first andsecond enclosures includes more than one cleaning dispensing unit.
 20. Awafer cleaning apparatus, comprising: a polishing unit for chemicalmechanical polishing (CMP) of a wafer and a first enclosure for brushcleaning, wherein the polishing unit for CMP is arranged to feed thewafer from an unload location of the polishing unit for CMP to the firstenclosure for brush cleaning; wherein the first enclosure for brushcleaning contains therein more than one cleaning dispensing unitarranged to receive the wafer from the unload location of the polishingunit, and each cleaning dispensing unit comprises a fluid jet arrangedto direct cleaning fluids toward a far edge of the wafer after the waferis transmitted from the polishing unit for CMP to the first enclosure;and a second enclosure arranged to receive the wafer from the firstenclosure for brush cleaning after the CMP, the second enclosurecontaining therein more than one cleaning dispensing unit arranged todirect cleaning fluids toward the far edge of the wafer after the CMP ofthe wafer, wherein each cleaning dispensing unit comprises a fluid jetthat uses a cleaning chemical having a pH range from about 2 to about13, the cleaning chemical having a surface tension in a range of about20 to about 70 dyne/cm, the cleaning chemical having a conductivity in arange of about 100 to about 4000 μs/cm.